Actually the original poster (digitaldc) is correct. Everest is 8.8 km above SEA LEVEL (which obviously cannot apply to Mars). To make a fair comparison with Olympus Mons you should ignore the water on earth and measure from its lowest point (the Mariana Trench, 10.9 km below sea level) and with this you get 19.7 km for Everest.
>which suggests that the Messenger is going into a retrograde direction. Isn't that unusual?
Well, not quite. Remember that the Earth's orbital speed is about 19 miles/second, so Messenger's orbital speed around the sun is only a small fraction less than than.
What you have to do in order to approach an object closer to the sun than you is lose the potential energy in your current orbit. This will drop you into a lower orbit which will have a greater velocity but lower potential energy. I haven't looked at the Messenger web site, but I wouldn't be surprised if NASA will be using Venus in a reverse slingshot (one that _loses_ energy) in order to get Messenger to Mercury.
Whaa? "2001: a Space Odyssey" was released in 1968. The Voyager probes reached Jupiter in 1979.
Arthur C. Clarke (who co-wrote the movie's sceenplay with Kubrick) explained in his book _the Lost Worlds of 2001_ that the reason why Discovery went only to Jupiter was that the expense of creating _two_ sets of images of gas giants was going to be very high, so they settled on creating just one.
Rats--another correction. I forgot to account for the time before the light hits the screen. The thing is is that the farther the observer gets from the screen, the closer the apparent expansion to 1 light-second in radius approaches sqrt(2) - 1.
Imagine this: You are two light-seconds away from a flash bulb. Halfway between you and that flash bulb there is a translucent screen of infinite extent perpendicular to the line between you and the bulb. Let the "center" of the screen be the point on the screen directly between you and bulb.
The flash bulb goes off and two seconds later you see the center of the screen light up. This expands into a ring as more of the screen is lit by the flash of the bulb. When the ring reaches one light-second in diameter, some basic trig will show that that light will take ~2.8 seconds to reach you. From your point of view the ring appears to have expanded to 1 light-second in radius in only 0.8 seconds.
Now if you move to 2000 light-seconds away from the screen then the APPARENT expansion is even more dramatic. From this point of view the center of the screen becomes lit at 2001 seconds after the flash bulb goes off, but the light ring reaches 1 light-second in diameter in only 2001.00025 seconds; thus it appears that ring has expanded to 1 light-second radius in 0.00025 seconds.
In that picture sequence what you are seeing is not an explosion of material from the burster but light from it being reflected by interstellar clouds. These clouds are a bit closer to us than the burster. The pathway from the burster to the outermost clouds in the last picture of the series is 8 light-months longer than the pathway to the clouds in the first picture.
A simplified model: Imagine a light and you are 2 light-seconds apart with a thin translucent screen halfway between you and the bulb, this screen being perpendicular to that path and of infinite extent. The light flashes on very briefly and you see the point of the wall directly between you and the bulb light up in 2 seconds. As you watch a ring forms around that point as screen is lit progressively by the burst of light. When the light travelling at a 45 degree angle off of the path directly to you hits the the screen, it forms a ring 1 light-second in radius. Some basic trig shows that the light from this ring gets to you in just over 2.8 seconds (2*sqrt(2)), thus the ring appears to have grown from the center point to 1 light-second radius in 0.8 seconds.
Move along--no violation of the speed of light here.
Nope. My off-the-cuff calculations show that the HST's resolution would be about 80 feet (25 meters) per pixel, so realistically the smallest object that the HST can resolve is about twice that in size.
If your objection is something like "But they can identify the brand of a cigarette pack in spy satellite pictures!"--well, sure, but they are looking from only 100-200 miles. The HST is looking at something over 1000 times further away.
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Here ya go. The energy drink chart even normalizes them to their caffiene content based on 12 oz. of liquid (though note that coffee and tea are not).
Tech Nation with Dr. Moira Gunn
http://www.technation.com/
Actually the original poster (digitaldc) is correct. Everest is 8.8 km above SEA LEVEL (which obviously cannot apply to Mars). To make a fair comparison with Olympus Mons you should ignore the water on earth and measure from its lowest point (the Mariana Trench, 10.9 km below sea level) and with this you get 19.7 km for Everest.
>which suggests that the Messenger is going into a retrograde direction. Isn't that unusual?
Well, not quite. Remember that the Earth's orbital speed is about 19 miles/second, so Messenger's orbital speed around the sun is only a small fraction less than than.
What you have to do in order to approach an object closer to the sun than you is lose the potential energy in your current orbit. This will drop you into a lower orbit which will have a greater velocity but lower potential energy. I haven't looked at the Messenger web site, but I wouldn't be surprised if NASA will be using Venus in a reverse slingshot (one that _loses_ energy) in order to get Messenger to Mercury.
Whaa? "2001: a Space Odyssey" was released in 1968. The Voyager probes reached Jupiter in 1979.
Arthur C. Clarke (who co-wrote the movie's sceenplay with Kubrick) explained in his book _the Lost Worlds of 2001_ that the reason why Discovery went only to Jupiter was that the expense of creating _two_ sets of images of gas giants was going to be very high, so they settled on creating just one.
Rats--another correction. I forgot to account for the time before the light hits the screen. The thing is is that the farther the observer gets from the screen, the closer the apparent expansion to 1 light-second in radius approaches sqrt(2) - 1.
ACK! Sorry: in the middle paragraph replace "the ring reaches one light-second in diameter" with "the ring reaches one light-second in radius"
Try here
Check the link to the highest quality images for a 19 MB JPEG and a 33 MB TIFF.
Lots of space pictures at the HubbleSite here.
Imagine this:
You are two light-seconds away from a flash bulb. Halfway between you and that flash bulb there is a translucent screen of infinite extent perpendicular to the line between you and the bulb. Let the "center" of the screen be the point on the screen directly between you and bulb.
The flash bulb goes off and two seconds later you see the center of the screen light up. This expands into a ring as more of the screen is lit by the flash of the bulb. When the ring reaches one light-second in diameter, some basic trig will show that that light will take ~2.8 seconds to reach you. From your point of view the ring appears to have expanded to 1 light-second in radius in only 0.8 seconds.
Now if you move to 2000 light-seconds away from the screen then the APPARENT expansion is even more dramatic. From this point of view the center of the screen becomes lit at 2001 seconds after the flash bulb goes off, but the light ring reaches 1 light-second in diameter in only 2001.00025 seconds; thus it appears that ring has expanded to 1 light-second radius in 0.00025 seconds.
In that picture sequence what you are seeing is not an explosion of material from the burster but light from it being reflected by interstellar clouds. These clouds are a bit closer to us than the burster. The pathway from the burster to the outermost clouds in the last picture of the series is 8 light-months longer than the pathway to the clouds in the first picture.
A simplified model:
Imagine a light and you are 2 light-seconds apart with a thin translucent screen halfway between you and the bulb, this screen being perpendicular to that path and of infinite extent. The light flashes on very briefly and you see the point of the wall directly between you and the bulb light up in 2 seconds. As you watch a ring forms around that point as screen is lit progressively by the burst of light. When the light travelling at a 45 degree angle off of the path directly to you hits the the screen, it forms a ring 1 light-second in radius. Some basic trig shows that the light from this ring gets to you in just over 2.8 seconds (2*sqrt(2)), thus the ring appears to have grown from the center point to 1 light-second radius in 0.8 seconds.
Move along--no violation of the speed of light here.
Nope. My off-the-cuff calculations show that the HST's resolution would be about 80 feet (25 meters) per pixel, so realistically the smallest object that the HST can resolve is about twice that in size.
If your objection is something like "But they can identify the brand of a cigarette pack in spy satellite pictures!"--well, sure, but they are looking from only 100-200 miles. The HST is looking at something over 1000 times further away.