Asteroid impact: higher probability of daylight or nightime hours?

Question

As the earth moves around the Sun, spining on it's axis as it goes, the front side of the earth (at that moment in time) would seem to be more likely to run into an asteroid. Is this correct? Is the probability less that an asteroid would "run up behind" the earth and hit from the "back side", at that moment in time? If true, wouldn't that mean that the highest probability of an asteroid impact would be during the hours of midnight to noon. Do you agree?

Several answers are very thoughful and thought-provoking. I will extend the answer period for more discussion.

Answer 1

I think the truth is the exact opposite.

Asteroids in solar orbits which cut across ours at an angle have only a tiny chance of impact, compared to the ones whose orbit almost coincides with ours for part of the way. These ones could either have longer orbits with aphelion outside us, and perihelion at almost our distance, or shorter orbits with aphelion near us, and perihelion well inside. Now when the long-orbit ones get close to us us, they are moving faster (because they have enough extra energy to move outwards again), so they are catching us up; whereas when the short-orbit ones get close to us, they are moving slower (because they are going to fall inwards again), so we are catching them up.

There must be lots more longer-orbit asteroids than shorter-orbit ones, because there is much more room for them, and more material out there initially for them to coalesce from. So the odds are that the big impact will be from be orbitally behind us; and since we orbit with our dusk terminator trailing, expect it within a few hours of sunset.

Answer 2

If an asteroid was going to hit the daylight side, it would have had to have passed inside the earth's orbit. And the closer that impact point is to the center of the daylight side, the closer that asteroid would have passed to the sun.

If we assume an even distribution of asteroids from all directions, but half of those pass close to the sun, and some of those are gravitationally pulled into the sun. That chance does not exist on the night side. So there is a lower chance of an asteroid hitting on the daylight side.

How much less of a chance? Well, the sun subtends about a half degree of arc in the sky. Suppose we say anything within 5 degrees either side would get pulled in (which is very generous). Then the fractional part of the sky from which asteroids would NOT come is about three-tenths of 1% (10^2/180^2). So if our assumptions are close, there is about a third of 1% less chance of the asteroid hitting on the daylight side - not much of a difference!

Your argument is thoughtful, but there are a few problems with the argument the way you phrase it. First, the 'back side' (in the circle we travel around the sun) and the 'front side' are both half daylight, half night. Second, asteroids travel faster than the earth's velocity around the sun, so they're still going to catch us as we're running away from them. So actually, although the difference is small, your main question (daylight) is the real difference, not your explanation (midnight to noon).

Answer 3

It really doesn't matter which way the world is facing.

Firstly... If a collision is going to occur, night or day make no difference, all that's needed is for two objects to occupy the same bit of space at the same time.

Secondly... it may be night time for half the world, but it's day for the other half.. the planet's motion doesn't change just because a given point on its surface faces the sun...

It's true that, if an object was moving in the same approximate direction as the planet, i.e, sneaking up from behind, its relative velocity would be less - until it was captured by the Earth's gravity.
A body coming "the other way" would hit us a lot faster, but the choice would simply be just how fast do you want to be wiped out?

Answer 4

I don't agree. Asteroids can come from any direction and are impervious to daylight or dark. The earth's gravitation pull is what attracts them - not light. Their orbit along with the earth's orbit plus gravity is what finally allows the collision. Review the NASA pictures of when the comet hit Jupiter - had nothing to do with light or dark. How do you have a front side to a sphere? Review the known facts about the impact in Siberia in 1906.

Answer 5

Midnight to noon is correct. However, an asteroid which is coming from the outer solar system would be moving faster than our planet (it would be near it's closest to the sun), so it could catch up to Earth at any time. The difference between the odds of a midnight to noon versus a noon to midnight encounter probably is not too much.

Answer 6

its more likely to hit on the dark side of the planet. Asteroids are more lightly to come from the outer parts of the solar system moving inward. In this case, it would hit the earth on the side not facing the sun. The reason for it not being the other way around is because if the asteroid is closer to the sun and earth, its more likely to get trapped by the sun's gravity and pulled into it.

Answer 7

You are correct that the earth is more likely to collide with an asteroid in the direction the earth is traveling. But the point on the earth closest to the direction that earth travels is always on the line between night and day at sunrise. So no difference between night and day. You will have a higher probability of in the hours around sunrise though.

sun
|
| light
v
earth ----> direction of earth's travel

Answer 8

I think your point is a good one. It is a fact that more meteors are visible after midnight, local time, because that is when you are heading into the wind, so to speak. But I believe the opposite is true for a major asteroid hit, simply because the major asteroids have orbits that are outside that of Earth, making them zoom in to the Earth from behind, so to speak.

Answer 9

During night time we are facing the outer side of the Earth orbit. Since most of the asteroids and space debris come from outside the Earth orbit, I bet there will be more probabilities of an impact by night.
But, when an object is "captured" by the Earth gravity and when it enters the atmosphere it may change its trajectory. Therefore also who is enjoying daylight will not be safe. Only statistically a little more safe.

Answer 10

It all depends on the angle of impact. There is nothing to prevent an asteroid impact whether inner or outer of Earth's orbit when revolving around the Sun.