How visible would a really big nuclear detonation be if set off on the surace of the moon?

General Questions
#1

Let’s say President Obama sets up a Department of Doing Awesome Things, and the first program is to detonate a huge thermonuclear weapon on the surface of the Moon, “just because it will be so awesome.” government sources state.

Let us further assume that NASA constructs a launch vehicle sufficient to carry an absolutely humongous, 80-megaton device to the Moon, and detonates this bad boy 200 metres above the surface of the Moon, on the Earth side; let us further assume it goes off at Earth night somewhere on the Moon’s terminator (the line between light and dark."

  1. Would I be able to see this 80-megaton explosion of awesome with the naked eye?

  2. If not, how good would a 6-inch backyard Dobsonian do me?

  3. What would it look like? There’s no atmosphere on the Moon so I assume in some key ways it would look very different from blowing it up on the Earth.

#2

We’ve done this before: http://boards.straightdope.com/sdmb/showthread.php?t=526701

#3

The largest nuclear bomb ever detonated was the Tsar Bomba.

Since THIS event was observed by people with no optical instruments; then yes, you’d see a bright, but small, flash.

With the Bomba, the flash is about 2.5Km across; in the second, the crater is about 40 Km across.

So, you’d see something.

#4

[SMARTASS] I actually came in here to find out what a “surace” was. [/SMARTASS]

#5

The moon is 238,000 miles away.

As noted even the biggest fireball from a nuke ever was about 5 miles in diameter. On the moon, with no air, I am not sure it would get that big (the fire ball is in fact fire and not nuclear which is over in a fraction of a second…no air, no fire).

But even if it were 5 miles in diameter that is pretty small at a range of 238,000 miles. You would not see it at all or at best it would be a pinprick of light for a short while.

I am willing to bet you’d see the initial flash of the explosion though.

#6

The diameter of the fireball doesn’t matter. Apart from the sun, there are no stars that subtend an angle large enough for us to distinguish them from a pure point. But the energy that comes from the point matters, and defines the brightness. (The difference between point source and extended sources makes thinking about the light grasp of telescopes slightly complicated.)

All that matters is the amount of visible light released, indeed, the longer the source remains an effective point source from the viewpoint of an Earth observer it is probably better.

A nuke will probably kick up and vaporise enough dust that will glow incandescently for some time to create quite a lot of light. With no atmosphere the only energy loss will be from radiation, so one might expect a longer glow than in an atmosphere. As noted above, the actual flash of light from the nuke itself will be mere microseconds long. But bright.

#7

This should be an episode of Mythbusters.

#8

It would blow their budget for the next several decades. But, IMHO, it would be worth it.

#9

Except after they prove/disprove the myth, they usually punch it up with *even more * explosives. :open_mouth:

#10

Only if they put the bomb on a treadmill and try to get it moving fast enough to launch itself to the moon.

#11

Well, the Alameda NAS isn’t used so much anymore these days. Perhaps constructing a launch pad would be good for the local economy.

#12

The fireball of a nuclear explosion is at first a ball of incandescent gas, and later a vortex ring.

In vacuum there is no persistent ball of incandescent gas, and certainly no ring vortex. No smoke either. In a vacuum, smoke becomes “hypervelocity beam of macroparticles”

So, a nuke in vacuum looks like a big flashbulb.

On the other hand, if it was detonated against the surace or underneath, the plume of incandescent solid material might give many seconds of brightness after the initial flash.

#13

Should I be disappointed that nobody has yet mentioned SPACE: 1999?

#14

Bombing the moon? The rabbits certainly won’t be happy about that.

#15

Marvin the Martian might like it :slight_smile:

#16

Yeah, but at some point we would see that handlebar mustache “flapping in the breeze” that we know doesnt exist on the moon and we would realize the whole thing was faked.

#17

Hey, gotta nuke something.