Last night I dreamed that something had a near miss of the Earth but nudged us out of stable orbit. Our end of days was going to be a fiery collision into the sun. In the dream, we only had about 10 days before the demise of the planet. I got to the part where the sun was huge, it was getting pretty warm and water was evaporating quickly. I woke up before anything happened though.

Obviously dream-physics are a bit off, but I was wondering how would we would die in that scenario? I think it’s likely to be due to heat rather than the lack of water first. And in a time span of 10 days before collision, about what day would we die? Day 3?

May I say that you have some of the weirdest dreams I have ever heard someone retell.

Try this book as a night time read and get back to us :P
The Age of Miracles, Karen Thompson Walker

Divine Angel said:

Last night I dreamed that something had a near miss of the Earth but nudged us out of stable orbit. Our end of days was going to be a fiery collision into the sun. In the dream, we only had about 10 days before the demise of the planet. I got to the part where the sun was huge, it was getting pretty warm and water was evaporating quickly. I woke up before anything happened though.

Obviously dream-physics are a bit off, but I was wondering how would we would die in that scenario? I think it’s likely to be due to heat rather than the lack of water first. And in a time span of 10 days before collision, about what day would we die? Day 3?

It would take a pretty big bump to knock us out of our orbit and send us on a collision course with the sun. So the initial contact would probably be enough to destroy most life on the planet. After that any change in our position relative to the sun would have an immediate effect on the weather would cause all sorts of havoc. Having survived all that, it would probably get very toasty, very quickly as we approached the sun.

kii said:

May I say that you have some of the weirdest dreams I have ever heard someone retell.

I wouldn’t. It isn’t uncommon to dream about things that your brain noticed that day.. and it was in the TV about a passing asteroid and attendant moon.

roughbarked said:

kii said:

May I say that you have some of the weirdest dreams I have ever heard someone retell.

I wouldn’t. It isn’t uncommon to dream about things that your brain noticed that day.. and it was in the TV about a passing asteroid and attendant moon.

Well, I do say it. Yes, I know that stuff about regurgitating the day’s events…but only DA’s brane seems to go to such extremes of dreaming.

in practical terms?

there’s not much that will take earth off its orbit of the sun – short of a collision that would have to smash the earth into a million pieces

if you’ve not dreamed of a collision then theres no problems

wookiemeister said:

in practical terms?

there’s not much that will take earth off its orbit of the sun – short of a collision that would have to smash the earth into a million pieces

if you’ve not dreamed of a collision then theres no problems

I’ve seen heaps of things at night that would make people have nightmares.. but luckily they were asleep, dreaming about food or sex.

roughbarked said:

wookiemeister said:

in practical terms?

there’s not much that will take earth off its orbit of the sun – short of a collision that would have to smash the earth into a million pieces

if you’ve not dreamed of a collision then theres no problems

I’ve seen heaps of things at night that would make people have nightmares.. but luckily they were asleep, dreaming about food or sex.

giant kangaroos

kangaroos sleep in the daytime.

I agree with diddly-squat. The impact (day 0) would be the moment of death. The impactor would likely be huge – really huge – and also have significant velocity. In any case, its kinetic energy (KE = 0.5mv^2) would need to be enormous for the impactor to change the path of the earth so much. This collision would destroy the planet, and its life.

Michael V said:

I agree with diddly-squat. The impact (day 0) would be the moment of death. The impactor would likely be huge – really huge – and also have significant velocity. In any case, its kinetic energy (KE = 0.5mv^2) would need to be enormous for the impactor to change the path of the earth so much. This collision would destroy the planet, and its life.

will it still be spectacular if no-one is around to see it?

Michael V said:

I agree with diddly-squat. The impact (day 0) would be the moment of death. The impactor would likely be huge – really huge – and also have significant velocity. In any case, its kinetic energy (KE = 0.5mv^2) would need to be enormous for the impactor to change the path of the earth so much. This collision would destroy the planet, and its life.

You never hear the bullet that hits you.

Arts said:

Michael V said:

I agree with diddly-squat. The impact (day 0) would be the moment of death. The impactor would likely be huge – really huge – and also have significant velocity. In any case, its kinetic energy (KE = 0.5mv^2) would need to be enormous for the impactor to change the path of the earth so much. This collision would destroy the planet, and its life.

will it still be spectacular if no-one is around to see it?

profound.

What colour will it be?

Arts said:

Michael V said:

I agree with diddly-squat. The impact (day 0) would be the moment of death. The impactor would likely be huge – really huge – and also have significant velocity. In any case, its kinetic energy (KE = 0.5mv^2) would need to be enormous for the impactor to change the path of the earth so much. This collision would destroy the planet, and its life.

will it still be spectacular if no-one is around to see it?

.

Mu.

That’s an awesome dream!

Michael V said:

I agree with diddly-squat. The impact (day 0) would be the moment of death. The impactor would likely be huge – really huge – and also have significant velocity. In any case, its kinetic energy (KE = 0.5mv^2) would need to be enormous for the impactor to change the path of the earth so much. This collision would destroy the planet, and its life.

I see what you did there…

;)

Well that’s an anticlimax.

Stoopid dream physics, I knew it was wrong…

So the only way the sun can kill you is skin cancer?

Well I read the OP incuding the bit where she said

Oops, hit the wrong button.

I meant to say

I read the OP including the bit where she said something massive had a near miss with Earth,
there’s no collision, just something big enough to drag us out if orbit.

Interesting thought. The tides would stop unless the moon came with us, apart from that, I guess it would just get hot.

If I had proper net access I’d look up a few figures and try to answer your question. With 10 days to work with it seems fairly straight forward to figure out where the Earth would have to be to extinguish bio processes.

pommiejohn said:

I read the OP including the bit where she said something massive had a near miss with Earth,
there’s no collision, just something big enough to drag us out if orbit.

The tides would stop unless the moon came with us,

Or get bigger.

Riff-in-Thyme said:

pommiejohn said:

I read the OP including the bit where she said something massive had a near miss with Earth,
there’s no collision, just something big enough to drag us out if orbit.

The tides would stop unless the moon came with us,

Or get bigger.

Good point. As we got closer to the sun, I guess they would get bigger. We might drown before we roasted.

pommiejohn said:

Oops, hit the wrong button.

I meant to say

I read the OP including the bit where she said something massive had a near miss with Earth,
there’s no collision, just something big enough to drag us out if orbit.

Interesting thought. The tides would stop unless the moon came with us, apart from that, I guess it would just get hot.

is that possible? how big would the something have to be to not touch the earth but to pull it out of orbit? bigger than the sun I suspect

Arts said:

is that possible? how big would the something have to be to not touch the earth but to pull it out of orbit? bigger than the sun I suspect

It’s a dream it doesn’t have to be possible :)

pommiejohn said:

Arts said:

is that possible? how big would the something have to be to not touch the earth but to pull it out of orbit? bigger than the sun I suspect

It’s a dream it doesn’t have to be possible :)

oh, in that case, we all die of boredom when the aliens read us thier poetry

their

stupid words

Divine Angel said:

Last night I dreamed that something had a near miss of the Earth but nudged us out of stable orbit. Our end of days was going to be a fiery collision into the sun. In the dream, we only had about 10 days before the demise of the planet.

To cause the Earth to fall into the Sun, you need to kill most of its orbital speed, which is around 30 km/s, giving a kinetic energy around 2.7 × 10^33 joules. Any interaction that was powerful enough to do that would make a mess of the planet: even if it was a near miss, the tidal effects would tend to rip the planet apart.

The gravitational binding energy of the Earth is approximately 2.487 × 10^32 joules. That’s the amount of energy required to overcome the gravity holding the planet together and throw all the bits out so fast that they won’t fall back together again (but it doesn’t take into account the chemical binding energy holding stuff together). Note that the orbital kinetic energy is ten times higher, so it’s not easy to stop the Earth without smashing it to smithereens.

But even if the Earth somehow survived the interaction, it’d probably take a lot longer than 10 days to reach the Sun. If the interaction “merely” killed our orbital speed so that we fell into the Sun, it’d take around 64 days to reach the Sun.
We’d cross the orbit of Venus in about 41 days, and the orbit of Mercury in about 56 days.

Of course, if the orbit-disrupting interaction pulled the Earth towards the Sun, then that time would be reduced, but such an interaction would require a lot more energy than the basic “stop the Earth in its tracks” interaction, so it’d do a lot more initial damage.

…

Some related xkcd forum threads
A (Simple?) Physics Problem

If the Earth was suddenly stopped in its orbit, what would happen on the surface? Wouldn’t we fly into space?

And
Blowing up the Earth more efficiently

To cause the Earth to fall into the Sun, you need to kill most of its orbital speed, which is around 30 km/s, giving a kinetic energy around 2.7 × 10^33 joules. Any interaction that was powerful enough to do that would make a mess of the planet: even if it was a near miss, the tidal effects would tend to rip the planet apart.
————————
A 1G retrorocket would only need fire for 50-odd minutes to stop us in our orbit (I think). Sure it is a big rocket, but 1G deceleration should be survivable.

http://curious.astro.cornell.edu/question.php?number=674

Around 65 days to fall into the sun apparently.

I guess that’s enough time for a lot of people to die of ‘social collapse’ before any intrinsic uninhabitability sets in.

Stealth said:

To cause the Earth to fall into the Sun, you need to kill most of its orbital speed, which is around 30 km/s, giving a kinetic energy around 2.7 × 10^33 joules. Any interaction that was powerful enough to do that would make a mess of the planet: even if it was a near miss, the tidal effects would tend to rip the planet apart.
————————
A 1G retrorocket would only need fire for 50-odd minutes to stop us in our orbit (I think). Sure it is a big rocket, but 1G deceleration should be survivable.

Fair enough. But we’re not using a rocket.

I guess you could kill our orbital speed during a near miss without massive tidal effects if the other body were far enough away, but them it’d have to be really massive. And its speed would need to be close to our (current) orbital speed so that the interaction lasted long enough, considering that the Earth (currently) travels a distance equal to its diameter in around 7 minutes.

Soso said:

http://curious.astro.cornell.edu/question.php?number=674

Around 65 days to fall into the sun apparently.

I guess that’s enough time for a lot of people to die of ‘social collapse’ before any intrinsic uninhabitability sets in.

That’s a very interesting article, thanks.

The various scenarios supplied as means to put the Earth on a collision course with Sol are fair enough but what is the answer to the simple scenario of the an intact Earth somehow being put on a trajectory that would provide a collision after 10 days?

There would have to be a point where the atmosphere would be stripped from the planet cause death by asphyxiation. Would this occur before temperatures extinguished life?

Divine Angel said:

Last night I dreamed that something had a near miss of the Earth but nudged us out of stable orbit. Our end of days was going to be a fiery collision into the sun. In the dream, we only had about 10 days before the demise of the planet. I got to the part where the sun was huge, it was getting pretty warm and water was evaporating quickly. I woke up before anything happened though.

Obviously dream-physics are a bit off, but I was wondering how would we would die in that scenario? I think it’s likely to be due to heat rather than the lack of water first. And in a time span of 10 days before collision, about what day would we die? Day 3?

The Lathe of Heaven

is a 1971 science fiction novel by Ursula K. Le Guin.
The plot revolves around a character whose dreams alter reality.

“Those whom heaven helps we call the sons of heaven.
They do not learn this by learning.
They do not work it by working.
They do not reason it by using reason.
To let understanding stop at what cannot be understood
is a high attainment.
Those who cannot do it will be
destroyed on the lathe of heaven.” – Chuang Tse.

Divine Angel said:

Last night I dreamed that something had a near miss of the Earth but nudged us out of stable orbit. Our end of days was going to be a fiery collision into the sun. In the dream, we only had about 10 days before the demise of the planet. I got to the part where the sun was huge, it was getting pretty warm and water was evaporating quickly. I woke up before anything happened though.

Obviously dream-physics are a bit off, but I was wondering how would we would die in that scenario? I think it’s likely to be due to heat rather than the lack of water first. And in a time span of 10 days before collision, about what day would we die? Day 3?

I used to be good at answering questions like these. Let’s see if I still am. I calculated recently the the solar system’s Oort Cloud was quite unlikely because since the time of the solar system’s formation, the probability of another star passing through the nearer part of the Oort Cloud exceeded 80%, and any such traverse would have had a catastrophic effect on the Oort Cloud.

Now let’s suppose that the destabilisation of the Earth’s orbit was due to an unrelated star passing closer in through the solar system than the above. If such a star was slightly smaller in mass than the Sun then its radiation would be much smaller and we would survive the initial stellar pass. The Earth’s orbit could easily be destabilised to the point where its innermost part is inside that of Venus, but it wouldn’t crash into the Sun itself.

An alternative would be if the solar system passed through a thick cloud of dust and gas. The hydrodynamic drag of the Earth moving in its orbit through this would cause the orbit to decay, causing it to spiral into the Sun, but slowly.

Now let’s set the origin of the loss of orbit aside and postulate as above an Earth travelling in towards the Sun. We can either assume a uniform velocity due to the original kick in the orbital direction or an acceleration of velocity due to the Sun’s gravity. I’m going to assume a uniform velocity.

The amount of energy received from the Sun is proportional to the inverse square of the distance from the Sun. The amount of energy radiated by the Earth is proportional to the surface temperature in Kelvin to the fourth power. Ignoring transient effects such as evaporation for the moment, the balance between energy received and that radiated means that the Earth’s surface temperature increases as the inverse square root of the orbital radius. So to a first approximation the average (day + night, equator to pole) surface temperature of the Earth is:

Day , Temperature(Celcius)
0 , 15
1 , 31
2 , 49
3 , 71
4 , 99
5 , 134
6 , 182
7 , 253
8 , 371
9 , 638

Even after day 9 we’re nowhere near melting the rocks of the Earth’s crust.

Evaporation of the oceans will cool this slightly, Can I determine by how much?
By day 4, 1% of the Earth’s oceans have evaporated, by day 7 that’s 6%, by day 8 that’s 13% and by day 9 it’s 40%.

Evaporation of the Earth’s oceans will tend to keep the surface temperature at 100 Celsius while the evaporation continues, so even by day 9 the average surface temperature on the Earth could still be very close to 100 Celsius.

What about death? Without air conditioning 50 Celsius over a sufficiently long time will cause serious burns. So that’s a death due to high temperature on about day 2. With air conditioning, a typical air conditioning temperature drop is about 12 Celsius which is half way through day 2.

mollwollfumble said:

Divine Angel said:

Last night I dreamed that something had a near miss of the Earth but nudged us out of stable orbit. Our end of days was going to be a fiery collision into the sun. In the dream, we only had about 10 days before the demise of the planet. I got to the part where the sun was huge, it was getting pretty warm and water was evaporating quickly. I woke up before anything happened though.

Obviously dream-physics are a bit off, but I was wondering how would we would die in that scenario? I think it’s likely to be due to heat rather than the lack of water first. And in a time span of 10 days before collision, about what day would we die? Day 3?

I used to be good at answering questions like these. Let’s see if I still am. I calculated recently the the solar system’s Oort Cloud was quite unlikely because since the time of the solar system’s formation, the probability of another star passing through the nearer part of the Oort Cloud exceeded 80%, and any such traverse would have had a catastrophic effect on the Oort Cloud.

Now let’s suppose that the destabilisation of the Earth’s orbit was due to an unrelated star passing closer in through the solar system than the above. If such a star was slightly smaller in mass than the Sun then its radiation would be much smaller and we would survive the initial stellar pass. The Earth’s orbit could easily be destabilised to the point where its innermost part is inside that of Venus, but it wouldn’t crash into the Sun itself.

An alternative would be if the solar system passed through a thick cloud of dust and gas. The hydrodynamic drag of the Earth moving in its orbit through this would cause the orbit to decay, causing it to spiral into the Sun, but slowly.

Now let’s set the origin of the loss of orbit aside and postulate as above an Earth travelling in towards the Sun. We can either assume a uniform velocity due to the original kick in the orbital direction or an acceleration of velocity due to the Sun’s gravity. I’m going to assume a uniform velocity.

The amount of energy received from the Sun is proportional to the inverse square of the distance from the Sun. The amount of energy radiated by the Earth is proportional to the surface temperature in Kelvin to the fourth power. Ignoring transient effects such as evaporation for the moment, the balance between energy received and that radiated means that the Earth’s surface temperature increases as the inverse square root of the orbital radius. So to a first approximation the average (day + night, equator to pole) surface temperature of the Earth is:

Day , Temperature(Celcius)
0 , 15
1 , 31
2 , 49
3 , 71
4 , 99
5 , 134
6 , 182
7 , 253
8 , 371
9 , 638

Even after day 9 we’re nowhere near melting the rocks of the Earth’s crust.

Evaporation of the oceans will cool this slightly, Can I determine by how much?
By day 4, 1% of the Earth’s oceans have evaporated, by day 7 that’s 6%, by day 8 that’s 13% and by day 9 it’s 40%.

Evaporation of the Earth’s oceans will tend to keep the surface temperature at 100 Celsius while the evaporation continues, so even by day 9 the average surface temperature on the Earth could still be very close to 100 Celsius.

What about death? Without air conditioning 50 Celsius over a sufficiently long time will cause serious burns. So that’s a death due to high temperature on about day 2. With air conditioning, a typical air conditioning temperature drop is about 12 Celsius which is half way through day 2.

What he said.

Well my sign is going to read “The End of The World is only 48 hours away(potentially)!!!!!!!!”

Skeptic Pete said:

mollwollfumble said:

Divine Angel said:

Last night I dreamed that something had a near miss of the Earth but nudged us out of stable orbit. Our end of days was going to be a fiery collision into the sun. In the dream, we only had about 10 days before the demise of the planet. I got to the part where the sun was huge, it was getting pretty warm and water was evaporating quickly. I woke up before anything happened though.

Obviously dream-physics are a bit off, but I was wondering how would we would die in that scenario? I think it’s likely to be due to heat rather than the lack of water first. And in a time span of 10 days before collision, about what day would we die? Day 3?

I used to be good at answering questions like these. Let’s see if I still am. I calculated recently the the solar system’s Oort Cloud was quite unlikely because since the time of the solar system’s formation, the probability of another star passing through the nearer part of the Oort Cloud exceeded 80%, and any such traverse would have had a catastrophic effect on the Oort Cloud.

Now let’s suppose that the destabilisation of the Earth’s orbit was due to an unrelated star passing closer in through the solar system than the above. If such a star was slightly smaller in mass than the Sun then its radiation would be much smaller and we would survive the initial stellar pass. The Earth’s orbit could easily be destabilised to the point where its innermost part is inside that of Venus, but it wouldn’t crash into the Sun itself.

An alternative would be if the solar system passed through a thick cloud of dust and gas. The hydrodynamic drag of the Earth moving in its orbit through this would cause the orbit to decay, causing it to spiral into the Sun, but slowly.

Now let’s set the origin of the loss of orbit aside and postulate as above an Earth travelling in towards the Sun. We can either assume a uniform velocity due to the original kick in the orbital direction or an acceleration of velocity due to the Sun’s gravity. I’m going to assume a uniform velocity.

The amount of energy received from the Sun is proportional to the inverse square of the distance from the Sun. The amount of energy radiated by the Earth is proportional to the surface temperature in Kelvin to the fourth power. Ignoring transient effects such as evaporation for the moment, the balance between energy received and that radiated means that the Earth’s surface temperature increases as the inverse square root of the orbital radius. So to a first approximation the average (day + night, equator to pole) surface temperature of the Earth is:

Day , Temperature(Celcius)
0 , 15
1 , 31
2 , 49
3 , 71
4 , 99
5 , 134
6 , 182
7 , 253
8 , 371
9 , 638

Even after day 9 we’re nowhere near melting the rocks of the Earth’s crust.

Evaporation of the oceans will cool this slightly, Can I determine by how much?
By day 4, 1% of the Earth’s oceans have evaporated, by day 7 that’s 6%, by day 8 that’s 13% and by day 9 it’s 40%.

Evaporation of the Earth’s oceans will tend to keep the surface temperature at 100 Celsius while the evaporation continues, so even by day 9 the average surface temperature on the Earth could still be very close to 100 Celsius.

What about death? Without air conditioning 50 Celsius over a sufficiently long time will cause serious burns. So that’s a death due to high temperature on about day 2. With air conditioning, a typical air conditioning temperature drop is about 12 Celsius which is half way through day 2.

What he said.

so we’ve got two days to get our shit together…

for the bonus round, if the Earth found itself travelling at the same speed away from the sun, how soon before temperatures became umanageable?

Riff-in-Thyme said:

for the bonus round, if the Earth found itself travelling at the same speed away from the sun, how soon before temperatures became umanageable?

As before, this is world average mean surface temperature.

Day , Temperature(Celsius)
0 , 15
1 , 2
2 , -10
3 , -20
4 , -30
5 , -38
6 , -45
7 , -52
8 , -58
9 , -64
10 , -69.

The situation with the freezing of the oceans with increasing distance from the Sun is not the inverse of ocean evaporation, because when water freezes its thermal conductivity decreases enormously, and this helps to keep the water below the ice sheet liquid. It would take a time measured in years not days to freeze any significant depth of ocean. So the latent heat of freezing water has a negligible effect on the Earth’s mean surface temperature.

Animals and plants protected by surface ice or snow could survive for a long time. Humans protected by burning petrol or diesel fuel could survive for a long time. These fuels tend to freeze at temperatures in the range of -60 to -40 Celsius, so life would get progressively more difficult through days 6 to 9.

The absolute survival limit for air-breathing creatures would be close to day 90 when the atmosphere ceases to be a gas and turns liquid.

mollwollfumble said:

The absolute survival limit for air-breathing creatures would be close to day 90 when the atmosphere ceases to be a gas and turns liquid.

That would be an alarming turn of events.

Quietly. With dignity.

That’s how we do things in this country. It’s why other countries admire us.

Riff-in-Thyme said:

for the bonus round, if the Earth found itself travelling at the same speed away from the sun, how soon before temperatures became umanageable?

Trying to get my head around this ‘same speed’ concept. If you rid the earth of its orbital velocity is will accelerate towards the sun with a positive value for its surge (m/s^3). But to say an equal speed away does it have positive or negative acceleration and/or surge???

Trying to get my head around this ‘same speed’ concept. If you rid the earth of its orbital velocity is will accelerate towards the sun with a positive value for its surge (m/s^3). But to say an equal speed away does it have positive or negative acceleration and/or surge???

if it speeds away from the sun at the same rate as it would going towards the sun then surely the accelerations will be the same? positive.

What would happen if, instead of a near-miss with earth, this wandering asteroid knocked the moon out of it’s orbit?

AussieDJ said:

What would happen if, instead of a near-miss with earth, this wandering asteroid knocked the moon out of it’s orbit?

Do you mean that the Moon gets hit hard enough to send it into the Sun, or at least give it enough speed to escape the Earth?

In that case, tides would get a lot smaller.
And there’d be no more eclipses. :)

Until recently, it was believed that the Moon was important for the axial stability of the Earth, but recent calculations indicate that the Moon’s effect on the direction of the Earth’s axis isn’t actually very significant.

PM 2Ring said:

AussieDJ said:

What would happen if, instead of a near-miss with earth, this wandering asteroid knocked the moon out of it’s orbit?

Do you mean that the Moon gets hit hard enough to send it into the Sun, or at least give it enough speed to escape the Earth?

In that case, tides would get a lot smaller.
And there’d be no more eclipses. :)

Until recently, it was believed that the Moon was important for the axial stability of the Earth, but recent calculations indicate that the Moon’s effect on the direction of the Earth’s axis isn’t actually very significant.

Bit of a relief. Axial stability is kinda important.

Riff-in-Thyme said:

PM 2Ring said:

AussieDJ said:

What would happen if, instead of a near-miss with earth, this wandering asteroid knocked the moon out of it’s orbit?

Do you mean that the Moon gets hit hard enough to send it into the Sun, or at least give it enough speed to escape the Earth?

In that case, tides would get a lot smaller.
And there’d be no more eclipses. :)

Until recently, it was believed that the Moon was important for the axial stability of the Earth, but recent calculations indicate that the Moon’s effect on the direction of the Earth’s axis isn’t actually very significant.

Bit of a relief. Axial stability is kinda important.

And what would be likely to occur if, instead of knocking the Moon out of it’s orbit and away from Earth, the opposite happened, and the Moon was knocked towards the Earth?

AussieDJ said:

Riff-in-Thyme said:

PM 2Ring said:

Do you mean that the Moon gets hit hard enough to send it into the Sun, or at least give it enough speed to escape the Earth?

In that case, tides would get a lot smaller.
And there’d be no more eclipses. :)

Until recently, it was believed that the Moon was important for the axial stability of the Earth, but recent calculations indicate that the Moon’s effect on the direction of the Earth’s axis isn’t actually very significant.

Bit of a relief. Axial stability is kinda important.

And what would be likely to occur if, instead of knocking the Moon out of it’s orbit and away from Earth, the opposite happened, and the Moon was knocked towards the Earth?

It would just orbit in an ellipse. Once a month the tides would be really big, and a fortnight later they wuold be really small.

PM 2Ring said:

The gravitational binding energy of the Earth is approximately 2.487 × 10^32 joules. That’s the amount of energy required to overcome the gravity holding the planet together and throw all the bits out so fast that they won’t fall back together again (but it doesn’t take into account the chemical binding energy holding stuff together). Note that the orbital kinetic energy is ten times higher, so it’s not easy to stop the Earth without smashing it to smithereens.

Are you sure about that? According to the virial theorem, for gravitationally bound systems, the average kinetic energy is (minus) half the average potential energy.

Stealth said:

Trying to get my head around this ‘same speed’ concept. If you rid the earth of its orbital velocity is will accelerate towards the sun with a positive value for its surge (m/s^3). But to say an equal speed away does it have positive or negative acceleration and/or surge???

Let v = radial velocity, v0 = initial radial velocity (as a result of the near-collision), a = acceleration due to the Sun’s gravity, t = time.

The v = v0 + a*t. My assumption, and it seems to be fairly valid in this case is v0 >> a*t. So then we can ignore a*t and take v = v0 = constant.

What would happen if, instead of a near-miss with earth, this wandering asteroid knocked the moon out of it’s orbit?

When you have time, read the science fiction book “Moonfall” by Jack McDevitt. A wandering asteroid of large mass from outside of the solar system hits and shatters the Moon. Most of the material from the Moon stays up in orbit, but there is one sizable chunk of Moon heading for impact with the Earth, nicknamed “possum” short for “possible impactor”. Gripping stuff.