Incredibly inane thoughts have occurred to me recently, and this one I can’t get rid of. Suppose a huge comet or something hit the Earth hard enough to push it back in its orbit by, say 2 degrees, would we all have to reset our watches by the 34 hours, 16 minutes and 18 seconds or so to account for the movement (let’s assume there are still digital watches left and people to wear them), or would the calender just be that far off?
And yes, I know that 2[sup]o[/sup] is not the right amount of time that I stated, but math is not my strong point.
The time of day is set by the rotation of the Earth. The position in the loop around the Sun determines the season. So you’d have to change your calendar, not your watch.
Yes, but moving Earth through its rotation around the sun, without Earth spinning about its axis will change the position of the sun. Imagine the planet isn’t rotating and move it one revolution about the sun, it’ll go through 1 day.
It should probably be noted that it would take a very special sort of meteor to move you perfectly back along the Earth’s elliptical and then swing around to push on the other side to put us all back at the same velocity along the course as we had been previous to the event.
Sorry for the hijack, and I realise there may be threads elsewhere dealing with this, but how much warning could we expect for an impending meteor collision with Earth, and how many places does the Space Lab hold? Would being in there even help, no matter how many tins of beans you had?
Anything from several months down to zero. It depends upon which direction the meteor comes from. A meteor approaching from the same direction as the sun would probably not be noticed until it hit us.
If we were hit, the Earth’s orbit would be changed. If hit by a very large object, it would be changed more than a small. The mass and velocity (direction and speed) of the object would determine the kind of change.
But if we were hit by an object large enough to make a substantual difference in future Earth time, the setting on your watch, if it didn’t melt or incinerate, would probably be the least of your worries.
Anything hitting the Earth with enough energy to change its orbit would certainly have enough energy to melt the Earth’s crust, which makes knowing the time of day/year rather less important than it was. Even if we miraculously prevent this from happening, the Earth now almost certainly has a different orbit and rotates at a different speed. You’d have to create a new calendar and new time units. Your watch would be useless.
Would have to create a new sundial as well? Or would a current one just mark the passage of the Sun across the sky at a different speed and still be functional?
Which of course, is the correct answer. The OP seems to be assuming that there’s some sort of constant force propelling the Earth along the current orbit.
If there were an impact sufficient enough to stop the Earth and knock it backwards, it’s not going to continue on its current orbit. Without running through lots of equations, (which I haven’t used in decades), my WAG is that that with the angular momentum disturbed, we’ll begin a one-way trip into that small, but increasingly larger yellow thing in the sky.
I guess it would depend on the angle of impact on how much of the rotation would retain or be enhanced, but the likelihood of a twenty-four-hour day on our new trajectory would be slim.
Either way, I’d look at diversifying from real estate, even if you have to sell at a loss.
No such impact is possible. The amount of energy it would take to do that exceeds both the structural and thermal capacity of the materials which compose the planet: Earth would be shattered into a bazillion molten pieces and a fair amount of vapor.
Anyway, mess around with it to see if you can get an asteroid to change the Earth’s orbit or rotation significantly. Any asteroid big enough to do that will also turn the Earth into molten goo. Watches then become extremely low on the priority list of any hypothetical survivors.
The latter. You’d redefine one solar hour as one-twelfth of the time it takes the Sun to cross the sky (yes, I know) on the date of either equinox… and you’d have to reestablish those same equinoces by observation, if the Earth got smacked hard enough to change its rotation or revolution.
Highly unlikely. AIUI, it takes more energy to fire something into the Sun than it does to fire it out of the Solar System. Change the Earth’s speed, and it’ll drop into a lower orbit and pick up more speed as it does so; actually falling all the way into the Sun is not on the cards.
The ISS has approximately enough life support for three people, and has to be continually re-supplied from Earth. But to address your other question, and the question behind your questions, it depends on the size of the object. If we’re talking about something of the size that killed the dinosaurs, it’s just conceivable that we might have no warning at all: Some very large rocks have passed uncomfortably close to the Earth before, and not been noticed until they were already leaving. We could, of course, ramp up our detection efforts considerably, but the public will to do so just isn’t there at present.
However, even if something like what killed the dinosaurs hit the Earth, we’re not dinosaurs. Humans (at least, some humans) would be perfectly safe right here on the surface. The dinosaurs weren’t killed by being bonked on the head by the big rock, they were killed by lack of food, from the cold temperatures that prevailed for a few years after the impact. But humans, unlike dinosaurs, can stockpile food for years at a time, and store seeds to be re-planted after spring comes again, and grow food in greenhouses even when it’s wintry outside, and otherwise cope with such situations. So in a dino-killer impact with several years’ warning, we’d be fine, and even in one with no warning at all, those folks who already have stockpiles of food, or who managed to quickly acquire them, would still survive.
