Apollo – Ten Things You Don’t Know About Hubble
Apollo, Hubble cannot see the Apollo artifacts on the Moon. This question is sent to me roughly once a month, and sometimes even more often: why don’t we shut up the people who think the Apollo Moon landings were faked by pointing Hubble at the Moon and taking pictures of the Apollo sites?
Well, one reason is that, duh, NASA and astronomers have better things to do than try to prove something blaringly obvious to people who would just claim the resulting images are faked anyway.
But also, Hubble cannot see the artifacts on the Moon! They’re way too small.
This surprises a lot of folks, since they’re used to seeing razor-sharp images of nebulae and galaxies. However, remember that while those objects may be far away, they are also very, very big. Light years across, maybe thousands of light years across. The remains of the lunar landers are only 4 meters across. That’s a tad smaller.
Sure, you say, but the Moon’s a lot closer, right? Yeah, it is, but it turns out it’s not close enough.
You can calculate how small an object a telescope can resolve (that is, see as more than just a one pixel wide dot) using really basic algebra. It depends mostly on the telescope’s mirror size. When you do this for Hubble, you get an angular measure of about 0.1 arcseconds, a tiny amount to be sure.
The Moon is 1800 arcseconds across, so 0.1 arcseconds corresponds to about 200 meters on the Moon! In other words, something has to be bigger than a football stadium on the Moon before Hubble can see it. It’s surprising, I know, but that’s how the math works out. The lunar lander is about 0.002 arcseconds in size, well beyond the capabilities of any normal telescope (go to that link above for more info on ways this still might work).
So really, the only — and best — way to see the Apollo artifacts is to go back to the Moon. Of course, the Moon hoax believers will still deny it’s real. Their refusal to see reality is cosmic in its proportions.
Even today, 19 years after Hubble’s launch, it’s not all that uncommon to hear a newscaster refer to “Hubble’s lens”. I once heard it used by an announcer on a science show produced by the Space Telescope Science Institute, the agency that runs Hubble! The thing is, Hubble doesn’t use a lens. It has a mirror.
Galileo used a telescope with a lens, as did everyone up until Isaac Newton. He was the genius who figured out that a properly shaped mirror could focus light as well, and has advantages over a lens: mirrors need only be ground on one side (lenses have two), and mirrors can be made larger than lenses because they can be supported all across their back side, while lenses must be supported around their circumference, where the glass is thinnest and most vulnerable.
Over a certain size, lenses are simply impractical, so mirrors are used. Hubble’s primary mirror is 2.4 meters across, about 8 feet. Although it’s the biggest mirror for astronomy ever lofted into space, it’s considered small by ground-based standards; many telescopes today have mirrors 4 or more meters across. The mammoth twin Keck ‘scopes in Hawaii have mirrors made of segments that total 10 meters across each!
It turns out the cameras on board Hubble use mirrors too. Why? Glass absorbs light. Not much, maybe 2% of the incident light, but that adds up. A lens has two surfaces, each of which reflect a little bit of light, so you lose more through a lens than with a mirror. Also, mirrors can be made to reflect light of different colors about the same, but lenses bend light at different colors differently. So all in all, doing it with mirrors makes a lot more sense.
However, there are lenses on board: they are used in the Fine Guidance Sensors, small telescopes that track stars with incredible accuracy and help keep Hubble locked onto to its targets.
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