Spacey, man.

All the elements in our bodies, save perhaps some of the hydrogen, was created in the nuclear furnaces of stars.

WOW, isn't it amazing that it takes exactly 1 day and 1 year? I mean it would be kind of messed up if it took longer or shorter.

It's 23:56 for a day. That's why we have leap years. The poles don't really have "days". That's spheres for ya.


The earth revolves in the opposite direction that it revolves around the sun. Without this kenetic "English" spin we would drift into the sun.

The moon is so heavy compared to the Earth that it is really the nexus between the Earth and moons rotation around each other that rotates around the sun. Without the moon we would fall away from the sun.

21-21.5% Oxygen in the atmosphere. This is the only real abnormal part of our planet. So much free standing oxygen is incredibly volatile and is especially rare. It could almost certainly only be found in this proportion on a planet with so much plant life.. It is calculated that if there was 23-24% oxygen flame would shoot out 30' from a Bic lighter, concrete would be flammable and the first lightning strike to hit the earth would set it's surface ablaze.




Ahk

Indeed. The Universe is a completely hostile place for life and it would take billions of chances for a planet to orbit a few millions years in the "sweet spot".

Lucky for us, there are trillions of stars with trillions of planets, so its not really an surprise.

What's the average wing velocity of an unladen swallow?

"Estimating the Airspeed Velocity of an Unladen Swallow
Hashing out the classic question with Strouhal numbers and simplified flight waveforms.
by Jonathan Corum

After spending some time last month trying to develop alternate graphic presentations for kinematic ratios in winged flight, I decided to try to answer one of the timeless questions of science: Just what is the airspeed velocity of an unladen swallow?

What do you mean, an African or European Swallow?
To begin with, I needed basic kinematic data on African and European swallow species.


South African Swallow
(Hirundo spilodera)
European Swallow
(Hirundo rustica)

Although 47 of the 74 worldwide swallow species are found in Africa,1 only two species are named after the continent: the West African Swallow (Hirundo domicella) and the South African Swallow (Hirundo spilodera), also known as the South African Cave Swallow.
Since the range of the South African Swallow extends only as far north as Zaire,2 I felt fairly confident that this was the non-migratory African species referred to in previous discussions of the comparative and cooperative weight-bearing capabilities of African and European swallows.3
Kinematic data for both African species was difficult to find, but the Barn or European Swallow (Hirundo rustica) has been studied intensively, and kinematic data for that species was readily available.


It’s a simple question of weight ratios
A 54-year survey of 26,285 European Swallows captured and released by the Avian Demography Unit of the University of Capetown finds that the average adult European swallow has a wing length of 12.2 cm and a body mass of 20.3 grams.

Because wing beat frequency and wing amplitude both scale with body mass, and flight kinematic data is available for at least 22 other bird species, it should be possible to estimate the frequency (f ) and amplitude (A) of the European Swallow by a comparison with similar species. With those two numbers, it will be possible to estimate airspeed (U).


In order to maintain airspeed velocity, a swallow needs to beat its wings forty-three times every second, right?
Actually, wrong. By comparing the European Swallow with bird species of similar body mass, we can estimate that the swallow beats its wings 18 times a second with an amplitude of 18 cm:

Species Body mass Frequency Amplitude
Zebra Finch      13 g 27 Hz 11 cm
European Swallow 20 g ≈ 18 Hz? ≈ 18 cm?
Downy Woodpecker 27 g 14 Hz 29 cm
Budgerigar       34 g 14 Hz 15 cm

Note that even the tiny Zebra Finch flaps its wings no more than 27 times a second while cruising.
If we ignore body mass and look only at bird species with a similar wingspan, we can estimate an average frequency of 14 beats per second and an amplitude of 23 cm:

Species Wingspan Frequency Amplitude
Budgerigar 27 cm 14 Hz 15 cm
European Swallow ≈ 28–30 cm ≈ 14 Hz? ≈ 23 cm?
Downy Woodpecker 31 cm 14 Hz 29 cm
European Starling 35 cm 14 Hz 26 cm

By averaging all 6 values, we can estimate that an average European Swallow flies at cruising speed with a frequency of roughly 15 beats per second, and an amplitude of roughly 22 cm.

Skip a bit, Brother
Last month’s article on The Strouhal Number in Cruising Flight showed how simplified flight waveforms that graph amplitude versus wavelength can be useful for visualizing the Strouhal ratio (fA/U), a dimensionless parameter that tends to fall in the range of 0.2–0.4 during efficient cruising flight.

For a European Swallow flying with our estimated wingbeat amplitude of 24 cm, the predicted pattern of cruising flight ranges from a Strouhal number (St) of 0.2:

... to a less efficient 0.4:

If the first diagram (St = 0.2) is accurate, then the cruising speed of the European Swallow would be roughly 16 meters per second (15 beats per second * 1.1 meters per beat). If the second diagram (St = 0.4) is accurate, then the cruising speed of the European Swallow would be closer to 8 meters per second (15 beats per second * 0.55 meters per beat).

If we settle on an intermediate Strouhal value of 0.3:


We can estimate the airspeed of the European Swallow to be roughly 11 meters per second (15 beats per second * 0.73 meters per beat).


Three shall be the number thou shalt count
Airspeed can also be predicted using a published formula. By inverting this midpoint Strouhal ratio of 0.3 (fA/U ≈ 0.3), Graham K. Taylor et al. show that as a rule of thumb, the speed of a flying animal is roughly 3 times frequency times amplitude (U ≈ 3fA).5


We now need only plug in the numbers:


U ≈ 3fA
f ≈ 15 (beats per second)
A ≈ 0.22 (meters per beat)
U ≈ 3*15*0.22 ≈ 9.9
... to estimate that the airspeed velocity of an unladen European Swallow is 10 meters per second.

Oh, yeah, I agree with that with some further study, it became clear that these estimates are accurate, though perhaps coincidental.
An actual study of two European Swallows flying in a low-turbulence wind tunnel in Lund, Sweden, shows that swallows flap their wings much slower than my estimate, at only 7–9 beats per second:
“Compared with other species of similar size, the swallow has quite low wingbeat frequency and relatively long wings.” 7
The maximum speed the birds could maintain was 13–14 meters per second, and although the Lund study does not discuss cruising flight in particular, the most efficient flapping (7 beats per second) occurred at an airspeed in the range of 8–11 meters per second, with an amplitude of 90–100° (17–19 cm).


And there was much rejoicing
Averaging the above numbers and plugging them in to the Strouhal equation for cruising flight (fA/U = 7 beats per second * 0.18 meters per beat / 9.5 meters per second) yields a Strouhal number of roughly 0.13:
... indicating a surprisingly efficient flight pattern falling well below the expected range of 0.2–0.4.

Although a definitive answer would of course require further measurements, published species-wide averages of wing length and body mass, initial Strouhal estimates based on those averages and cross-species comparisons, the Lund wind tunnel study of birds flying at a range of speeds, and revised Strouhal numbers based on that study all lead me to estimate that the average cruising airspeed velocity of an unladen European Swallow is roughly 11 meters per second, or 24 miles an hour."

Fragile is all relative. IMO, each life from would have it's own set of unique circumstances. For instance, it's possible that something evolved with very high temperatures. Our comfortable temperature range could freeze them to death.

I think it's a high probability that something evolved somewhere, at some point, many times before and many times to come. Chances are, we may not even realize it if our paths ever cross.

Like I said we can't even really communicate with dolphins, and there is no doubt that they're intelligent and use language. Somehow I find it hard to believe that we will be capable of understanding extraterrestrials when we haven't figured it out for a species that we evolved next to.

I here the Halo games always have a great story line...

But I would have to buy an XBOX360 to enjoy them, which just isn't affordable at the moment.