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If something MASSIVE were to be near Earth

Nograts

Nograts

Platinum Member
And it was traveling pretty fast, would it appear to be moving slowly?

Say a giant alien ship, the size of Texas, was traveling across the sky really fast, would it appear to be moving slowly?

Or like a tidal wave from an asteroid impact coming towards you, it would be say 50 miles high and moving faster than the speed of sound would it look slow?
 
disappoint said:
No it wouldn't.
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Hrm....I was curious about this today while I was at a stop light. I was watching cars pass by and guessing their speed, which I would estimate to be within ~5-10mph of accuracy.

But then I saw a plane, and as it was making its descent I was guestimating its speed at over 200mph, possibly more (it was still a fair bit away from the airport), but it appeared to be moving pretty slowly.... a plane is pretty small relative to what I was proposing, but it got me thinking.
 
You still don't get it.

Let's say that an Earth-sized object was traveling the exact same speed as Earth goes around the sun: 67,000 MPH. Now, let's say that it wasn't orbiting the sun itself and was somehow traveling in a straight line that just happened to fall alongside our circular orbit at the same speed. If it also happened to be going the same direction as us, it would be perfectly still relative to us and the same 67,000 MPH relative to the sun. If it happened to be going the opposite direction then we would be going 134,000 MPH relative to each other!

Get it?

Also, you fail to consider just how far away in "the sky" this Texas-sized object would be. "The sky" is not a fixed height. The moon is much farther away than our space stations and satellites. How still it appears at a certain speed is directly proportional to how much of your field of view it occupies. If it were at the moon's distance, you wouldn't be able to see it at all, much less, track it's movement. Hell, if it was at Alpha Centauri, you wouldn't be able to detect its movement at all beyond the relative movement of all stars and stars are most certainly part of the "sky."
 
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Elevenpog said:
Hrm....I was curious about this today while I was at a stop light. I was watching cars pass by and guessing their speed, which I would estimate to be within ~5-10mph of accuracy.

But then I saw a plane, and as it was making its descent I was guestimating its speed at over 200mph, possibly more (it was still a fair bit away from the airport), but it appeared to be moving pretty slowly.... a plane is pretty small relative to what I was proposing, but it got me thinking.
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The plane was further away from you than the cars passing by, thus it appeared to be moving slowly because of it's distance from you.
 
disappoint said:
The plane was further away from you than the cars passing by, thus it appeared to be moving slowly because of it's distance from you.
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Okay so let's say a massive giant is in space, and his size is so big that the entire sky is his eyeball. He is pretty far away (much much further than the plane), but all you can see from where you're standing is his eye. He blinks just as you and I do.

Would that blink appear very slow to me on the ground, or happen in the blink of an eye (no pun intended)
 
Elevenpog said:
Okay so let's say a massive giant is in space, and his size is so big that the entire sky is his eyeball. He is pretty far away (much much further than the plane), but all you can see from where you're standing is his eye. He blinks just as you and I do.

Would that blink appear very slow to me on the ground, or happen in the blink of an eye (no pun intended)
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It might help to arbitrarily pick some numbers.

Let's say his eye is 1 billion light years in diameter. It would take billions of years for him to complete one blink of an eye considering he would have to blink slower than the speed of light. So the blink would appear to move very slowly even if he could blink at almost the speed of light.

He absolutely does not blink like you and I do though.

Things farther away have to cover more distance to traverse your field of view which is why they appear to move slowly even if they are moving fast.

Incidentally if you had a zoom lens or telescope your field of view would change even though your position and distance don't. The appearance of speed would increase. That is to say it would appear to move faster than without the zoom lens.

That is why you need image stabilization for zoom lenses. Your hand's shakes are "amplified" due to a change in field of view.
 
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disappoint said:
It might help to arbitrarily pick some numbers.

Let's say his eye is 1 billion light years in diameter. It would take billions of years for him to complete one blink of an eye considering he would have to blink slower than the speed of light. So the blink would appear to move very slowly even if he could blink at almost the speed of light.

He absolutely does not blink like you and I do though.

Things farther away have to cover more distance to traverse your field of view which is why they appear to move slowly even if they are moving fast.

Incidentally if you had a zoom lens or telescope your field of view would change even though your position and distance don't. The appearance of speed would increase. That is to say it would appear to move faster than without the zoom lens.

That is why you need image stabilization for zoom lenses. Your hand's shakes are "amplified" due to a change in field of view.
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Ah okay that makes a bit more sense then. So, in the case of ants looking at us then, we do move slower than we are actually moving, just not by much because our actual distance is only .000000000000000000000001 nano-light meters away?
 
Elevenpog said:
Ah okay that makes a bit more sense then. So, in the case of ants looking at us then, we do move slower than we are actually moving, just not by much because our actual distance is only .000000000000000000000001 nano-light meters away?
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It depends on the ant's field of view and the distance from the object they are viewing. Objects further away appear to be moving more slowly.
 
Elevenpog said:
And it was traveling pretty fast, would it appear to be moving slowly?

Say a giant alien ship, the size of Texas, was traveling across the sky really fast, would it appear to be moving slowly?
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Depends if said ship was on a treadmill.
 
Does the moon look like it's moving fast? It's going 2,288 miles per hour around the earth.It's 7-1/3 x 10^22 Kg
 
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Take an airplane flying through the sky directly above you. If you somehow had control over the moment-to-moment size, altitude, and speed of the airplane it would be possible to make the airplane get much bigger, much higher, and fly much faster without being able to see any difference from your ground perspective.
 
Speeds of 'space stuff' measured relative to the ground are never going to make much sense.

On a random note, 'SpaceEngine' is really cool and deserves its own thread if it hasn't had one. It allowed me to comprehend that the Trek-ian 'stars fly past you as you fly through space' thing is actually possible...if you go fast enough.
 
Elevenpog said:
Okay so let's say a massive giant is in space, and his size is so big that the entire sky is his eyeball. He is pretty far away (much much further than the plane), but all you can see from where you're standing is his eye. He blinks just as you and I do.

Would that blink appear very slow to me on the ground, or happen in the blink of an eye (no pun intended)
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viewing azathoth would drive you insane instantaneously
 
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