I wondered that same thing and did a bit of reading about it. My understanding is that Type Ia SNe’s are not all exactly the same brightness, but they can be normalized by measuring how long they take to fade.
From what I’ve read, a Type Ia SNe triggered by a PBH, compared to the usual trigger of accreting gas from a binary companion, would fade faster and observed brightness can be normalized to get an accurate distance measurement.
If your current plan is to buy the latest and greatest phone today, sell it in two years, and then buy a new top of the line phone, then Apple’s new lease program looks like an attractive option. They’ve priced it such that, over the course of the lease, you end up paying about the cost of purchasing the phone minus its resale value. Leasing looks convenient because it saves you from having to find a buyer.
It also keeps phones out of the secondary market, which benefits Apple. Off lease phones are used for warranty replacements, or sold as refurbished through official storefronts instead of person to person.
That’s true for older magnetorquers, because the Earth’s magnetic field is smooth enough that the difference between field strength at the top and bottom of the satellite is insignificant.
With superconductors you can scale up the magnetic field strength enough to get a usable net linear force.
2 big galaxies collided and shattered into a string of 12 small galaxies.
The dark matter is split unevenly among those 12 small galaxies in an hour-glass shaped distribution: very little in the middle of the string, and most of the dark matter concentrated at the ends.
I love the Kerbal-esque architecture of this mission.
-An ion drive stage drops it down a deep hole, toward the sun, then spends all its fuel slowing down almost enough to be captured by Mercury’s gravity instead of just flying by it at screaming fast speed. The empty fuel tanks and ion engines get thrown away when they’re used up.
-Then one of the stacked probes turns on its chemical engines for the capture burn, and it ditches some of its sun screen.
-When its just barely captured in a highly elliptical polar orbit, it releases a satellite equipped with its own independent systems.
-Then it maneuvers to a lower orbit that’s optimal for the other satellite.
Mercury is hard to get to, and only one other space craft has ever orbited it: MESSENGER. Now there will be 2 more delivered with a single launch.
Finding a dictionary on an asteroid would be pretty impressive, ngl.
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Locking in the gains and taking time to reload and refuel before round 2.
It was also rotated 90 degrees for some reason? The river is on the south side of the community.
The writing and atmosphere is better in New Vegas, but the gunplay is better in 4.
The cease fire was broken on day one when USA blockaded the ports, Iran demanded ships pay tolls for passing through the strait, and Israel and Hezbollah never got the memo to stop shooting at each other.
‘Negotiating’ in those conditions is performative at best.
PBH with mass <10^6g would have evaporated before the universe had cooled enough for atoms to form. Its possible they didn’t fully evaporate, but instead became “Plank relics”, which are a dark matter candidate.
PBH with mass 10^7g to 10^16g would have evaporated already, producing a background of gamma rays and gravity waves that we don’t see.
PBH with mass 10^17g to 10^22g would still exist today, and the gravity waves they generate are too small to be detected by current detectors. These are also a dark matter candidate.
PBH with mass >10^23, in sufficient numbers to explain the existence of dark matter, would cause gravity lensing that we don’t observe.
So according to observations, if the early universe produced PBH, they didn’t have an even distribution of masses from giant to tiny. Either they were all tiny (<1 ton), or they were all medium size (asteroid mass).
My favorite explanation of dark matter is the formation of asteroid mass PBHs when the early universe went through the phase change that separated the electroweak force into the electromagnetic force & nuclear weak force. Just a bit before electroweak symmetry breaking, the universe was in a state of supercooled false vacuum, and then bubbles of today’s vacuum energy started expanding. The pockets of false vacuum between the expanding bubbles of true vacuum would be slower to inflate, causing their density to grow relative to the rest of the universe, until they collapse into PBH. Because they’re all formed at the same time, from similar size pockets of similar density plasma, the resulting population of PBH are uniformly asteroid mass rather than having a Gaussian mass distribution.
Further reading:
Gaussian Planck Relics are Ruled-Out as Dark Matter by LIGO
Constraints on primordial black holes from the Galactic gamma-ray background
18,000 km/s
H A U L I N G A S S ! ! !
Each is moving at ~6% of the speed of light!
The paper linked to in the article says the thrusters have a specific impulse of 600s, and a thrust-to-power ratio of about 50 mN/kW.
Compared to the xenon ion thrusters used on the Dawn spacecraft, these new multi-mode thrusters produce more thrust, but are significantly less efficient. Dawn’s thrusters have a specific impulse of 3,100s and a thrust-to-power ratio of about 36 mN/kW.
Even so, it means satellites can be built with one small fuel tank that can power high efficiency electrospray thrusters to make slow maneuvers, or use the same fuel as a monopropellant to quickly get out of (or into) the way of something. ASCENT monopropellant thrusters can have a specific impulse slightly better (240 Isp) than traditional hydrazine monopropellant thrusters (235 Isp).
To be fair, primordial black holes are a candidate for explaining what dark matter is.
…There is a range of masses, , usually described as the ‘asteroid mass window’, where PBHs can make up all of the DM…
source: https://www.sciencedirect.com/science/article/pii/S0550321324000609
Went to school as an elvish impersonator.
Maybe the “Epstine didn’t kill himself” people will have something to say about that.
Remember when Tylenol was linked to autism, crashing the stock price of its maker just long enough for that business to be acquired at a steep discount by its new owner? And how we never heard about a link between Tylenol and autism again?
I wonder which vaccine maker is about to get a hostile takeover?