Tag Archives: space exploration

What would you weigh on an exoplanet?

picture of an exoplanetI was reading an article from somebody, all enthusiastic about the exo-planets the Kepler probe keeps finding. They’re all many times larger than planet Earth even if they’re in the ‘Goldilocks’ zone. You know the one – not too close, not too far, just right. That is, a planet neither too close to its primary nor too far away, where liquid water could exist. My immediate reaction was ‘sure, but we’d weigh too much’.

Then I began to wonder how much more. I’m not a mathematician – never have been. In truth, I can’t add up to save my life. So I’m counting on you (ha ha) to correct me if I get this wrong.

I discovered this site http://www.exploratorium.edu/ronh/weight/ and learned that gravitational pull weakens by the radius squared. So let’s say you weighed 60kg on planet Earth. Planet Gliese 581g is estimated at 2.6 Earth masses and 1.4 Earth radii. So yes, you’re going to weigh more on Gliese 581g, but not 2.6 times as much. If I’ve got this right, the increased diameter of the planet means you’ll weigh about 1.3 times as much – so about 78kg. That’s certainly not a huge imposition. And all of a sudden, I’m bouncing in my chair, going oooh oooh.

Here’s some estimated figures about Gliese 581g, taken from this fascinating website http://phl.upr.edu/projects/habitable-exoplanets-catalog

Mass = 2.6 Earth Radius = 1.4 Earth  Temp = average surface temperature, so this place, at 10, is rather cooler than our 15 degrees (NASA’s figure from 2008), but the estimate of average temperature assumes an Earth-like atmosphere, which is a pretty big assumption. On the face of it the planet zips around its sun in a fraction of the time it takes ours, taking only 32 days as compared to 365. But that might not be the case, since the Gliesean day may be much longer than Earth’s. The figures don’t mention period of rotation, which I find a tad surprising. As a comparison, Venus’s ‘day” (the time it takes to rotate on its axis) is actually longer than its year (the time it takes to orbit the Sun.) (http://www.universetoday.com/14282/how-long-is-a-day-on-venus/)

So there you have it. I found out today that a candidate for Torreno (capital of the Coalition of Worlds in Morgan’s Choice) may be only 20.2 light years away. And with the shift drive of the future, that’ll be a place to add to your holiday plans.

Ain’t science grand?

An unforgettable milestone in the journey of life

I woke this morning to the news that Neil Armstrong had passed away.

To me, that means two things; the end of an era and that unenviable feeling of being old. The things I’ve seen, the things that are a part of the parade of my life. On Twitter I learned a friend’s husband had been born just before that day in 1969; on Facebook another friend talked about reading a book about 9/11 and mentioned that there are teenagers around who were babies when the twin towers came down. So true. Milestones in the wheel of life. And sure, there are days, like JFK’s death, 9/11, the Japanese earthquake, Chernobyl, that are etched into my brain with acid. But the ones I look back on with pleasure and pride are the space days.

I was 18 when Apollo 11 left for the moon, in my second year of a BA degree in history. Like many of my colleagues, I stayed home to watch history being made. The whole western world quivered with excitement. President Kennedy’s goal of a man on the moon within a decade was about to be fulfilled. We’d seen the dark side of the moon from Apollo 10 (and the Russian probes, but we won’t go there). And now it was all about to happen. You’ve all seen the pictures as the three men in their bulky suits took their last walk to the tiny, tiny module on the top of the Saturn V rocket. So did we, on CRT TVs.

Now was the day, morning in Perth, Australia, and I sat on the edge of my seat in the lounge room, eyes glued on the TV while on the other side of Australia the signals came in to Parkes. We never knew, of course, that Armstrong had taken over landing the module himself, looking for a flat piece of Moon. Never knew he had 30 seconds of fuel left. That came out later. I peered at grainy black-and-white footage. First, the lander’s leg resolved itself and then you could just make out the ladder. Then a boot appeared and Armstrong eased his body down onto an unknown surface and uttered his famous words, ‘that’s one small step for man, one giant leap for mankind’. Even then I wondered how long he’d been rehearsing; and who had written it for him. Here’s the footage

The next few days went by in a blur of extra-terrestrial shots of footprints on an ancient landscape, attempts to raise a US flag fitted with an arm because there was no wind, the famous photo of the moon reflected in a visor. Buzz Aldrin and Neil Armstrong cavorted like a couple of kids in the weak gravity, while Collins stayed up there in the capsule. I held my breath on that final day when they blasted off to dock with the capsule and cheered when they splashed down in the Pacific.

By Source, Fair use, https://en.wikipedia.org/w/index.php?curid=1893642

It was years later before we all began to realise how dangerous the whole thing had been. These men were pawns in a race with the USSR – which had its own pawns, of course. NASA took a lot of risks and I’ll bet Mission Control had its fingers crossed many a time. What happened on Apollo 13 is a case in point. If you don’t know, go see the excellent movie of the same name, starring Tom Hanks. So the USA won the race. But interest waned quickly; the last manned flight, Apollo 17, was in 1972 and we don’t look like going back any time soon.

But Neil Armstrong’s name is in the history books forever. A brave but humble man who stood on the edge of eternity.