Knowledge

If I shine a flashlight at Mars, does a small amount of the light actually reach it?

Let’s say you had a very nice flashlight with a 5 degree beamspread and a 1 watt visible beam.

At 60 million km to Mars at close approach, the beam spreads out over 2.5××101313 sq km or 2.5××101919 sq meters. That means about 1 photon per second per square meter arrives at Mars.

Mars does not move far enough in the time it takes light to get there to need a lead ahead angle with a flashlight. If you were using a narrowbeam laser, you would need to calculate and precisely apply a lead ahead angle.

So yes, a very small amount of the light gets there. Not enough to detect with even advanced sensors, but some gets there.

I assumed a clear line of sight to Mars. No clouds, no volcanic dust in the air. You can subtract about 10% for atmospheric extinction in the Earth’s atmosphere. You can subtract a lot more if Mars is very close to the horizon as seen from your position. I also did not take the light through the Martian atmosphere to the Martian surface.

You can lose upwards of 90% of the light getting through the Martian atmosphere. None of that changes the basic answer. Yes, some light gets there, but it is below a detectable level.

Related Posts

What’s it like inside an aircraft carrier during a heavy storm?

During my time on a carrier, we went through a hurricane not once, but twice. We were in the Atlantic returning to our home port but first, we…

If the Soviets had decided to push the Allies out of Western Europe at the end of WW2, could they have done it?

Stalin asked Marshal Zhukov that very question in 1945. His answer: No. Westerns have a myth about the Red Army being this enormous inexhaustible machine that steamrolled its…

How long can an Ohio-class submarine stay submerged?

The Ohio-class nuclear submarine was designed for extended strategic deterrent patrols. Each submarine is assigned two complete crews, called the Blue crew and the Gold crew, each typically serving…

Why is the F-35 terribly flawed but the F-22 wasn’t?

The F-35 has been clubbing F-15s, F-16s, F-18s, like baby seals in recent exercises. And In Red Flag 17–1 when the F-35 was declared out of weapons, the…

How large can an aircraft carrier be made to accommodate as many aircraft as possible?

HMS Habakukk was planned to be 2000′ long, 300′ wide, and able to carry 200 planes including heavy bombers! While it was theoretically possible to build it, the…

Which US Navy jet was the most difficult or the easiest to land on the Aircraft Carrier?

Most difficult or worst? Almost certainly the Voight F7U Cutlass. 25% of the production run was lost to landing accident. Carrier Captains started ordering them off their ships…