Why is this better than launching a telescope into orbit?
Hubble has a 2.4 meter mirror, TMT is 30 meters. Resolution scales with the diameter of the mirror (so an order of magnitude more for TMT), while light gathering scales with the area (two orders of magnitude more for TMT).
Traditionally, there were two challenges for large ground based telescopes: a) We couldn't make telescope mirrors larger than ~5 meters because the glass starts to deform under its own weight and the view gets worse rather than better; and b) we lose too much to atmospheric distortion.
The solution to the first issue is to assemble large mirrors from many small mirrors in a honeycomb pattern[0].
The solution to the second one is adaptive optics[1]: Actuators and computer control can compensate for atmospheric distortion by precisely deforming the mirror in real time, several times per second, to cancel out the distortion. We still need a good location for the telescope to minimize the amount of distortion we need to handle, but with that we could for the first time achieve better resolution from the ground with the 10-meter Keck.
These days the benefits of a space telescope come not so much from visible light, but from other wavelengths that are fully or partially blocked by the atmosphere[2]. Like UV, X-ray, or infrared like the upcoming James Webb space telescope.
[0] https://www.wired.com/2008/10/in-the-late-197/
[1] https://en.wikipedia.org/wiki/Adaptive_optics
[2] http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson2-1...
It sure is a lot cheaper to go to Mauna Kea than space though.
/joke
As much as I’m automatically inclined to side with science over mysticism, there are other telescopes being built right now (ELT, GMT) in the same class, both in Chile, where the mountains aren’t sacred, but just mountains.
So - while they’re pushing on for now, it seems there’s as much dogma (we must have this telescope here) amongst scientists as their is amongst the spiritualists - yes, the top of Hawaii is a uniquely good spot for a telescope - within US borders - there are other spots just as good, however, but those would require international negotiation and cooperation rather than just domestic negotiation and cooperation.
It all comes down to cost/benefit, and I think it’s getting marginal for the TMT. They’re going to need round the clock security, as the protests won’t stop once it’s built.
It’s not too late to build it elsewhere - even in space. Launch costs have dropped dramatically since the TMT was conceived, and are continuing to do so. Assembly will then be the tricky part, as with JWST.
ELT 2025 (39.3m, 978m²)
TMT 2027 (30m, 655m²)
(Future first-light dates are provisional and likely to change. https://en.wikipedia.org/wiki/Extremely_Large_Telescope)
Nice mirror size comparison: https://en.wikipedia.org/wiki/Extremely_Large_Telescope#/med...
It’s totally been worth it though.
Stepping stones - if the new class of earth based telescopes finds something worth looking at, there will be space telescopes that make the JWST look like a toy - but not for a while yet. This is basically the “cheap” trial experiment.
The total eva time for all five servicing missions for Hubble is under 200 hours.
Meanwhile, this observatory will be much more easily accessible and will therefore have a lifetime many times that of the Hubble - and can become a museum after its lifetime.
The expanded light-gathering capability of a thirty meter aperture combined with the great conditions that exist at the top of Mauna Kea because of its altitudes will allow for a lot of observations that would've been impossible before because the data produced wouldn't have been clear enough.
The light gathering power will be greater than any current instrument. The spatial resolution will be better than any current non-interferometric system. The adaptive optics are in a new league, and the mirror coatings will allow a very broad spectrum to be sensed.
But what will we discover? We honestly don’t know. It’s been a bit of a bone of contention as many in science would argue that you should define your goals and then devise the experiment and apparatus - but cosmology and astronomy are a bit different, as most of the huge discoveries have been utterly unexpected, and have “just happened” as a result of better telescopes and observations, from moons of other planets to heliocentricism to other galaxies to red shift to the Big Bang to quasars and pulsars - we didn’t expect any of these things, we just found them.
So that’s the improvement - hopefully new science, new discoveries.
I'm a bit skeptical of this particular claim as the existing telescopes haven't needed round the clock security. Generally speaking, I never felt the telescopes were as controversial as is made out. Rather, the opposition is a small, but very vocal minority. That said, I can see why TMT is particularly contentious as any new construction is an obvious point of resistance, and TMT is so much larger than the existing telescopes.
I can’t imagine UH doing what the protectors are asking and simply plonk the TMT in a completely different ocean.
TMT is the only planned 30m class telescope in the northern hemisphere at the moment.
Longitudinal placement is also important for tracking transient phenomena such as FRB’s and NEO’s. this is why Hawaii is such a critical location for doing optical observations.
I would not be surprised if the Chinese build a thirty meter class telescope at some stage. Not sure where though?
Or near Skardu, Pakistan? https://en.wikipedia.org/wiki/Skardu
On the high Tibetan plateau somewhere not very far from this airport?
Additionally, Hawaii has strict rules about light pollution, and street lights designed not to disrupt the telescopes.
Sites in the middle of mountain ranges aren't necessarily any good - you have to see what's upwind of the site. The high plains near Denver, CO are no good because the Rockies are upwind, for example.
The technical term in astronomy circles is "seeing" if you want to learn more.
On top of that building a telescope with a very large mirror is much harder because they have to be launched. The mirror on James Webb is only 6.5m (ish) and it requires a folding mechanism to fit inside the faring of rockets. Making a 30m mirror may not be possible without going to farings larger than any rocket around today. BFR if it actually pans out will make much larger space telescopes possible.
When you build something to go to space it gets way more expensive. Hubble cost around $4billion before it launched, JWST is gonna cost more than $10b, and WFIRST, a relatively cheap space telescope, will cost at least $3 billion.
The most expensive telescope on Earth only cost about $1 billion. It weights about 15 million pounds, so just the launch costs to put it in orbit would exceed the $1 billion it cost to build.