- Susskind & Harbovsky, The Theoretical Minimum: what you need to know to start doing physics (pdf)
- Michio Kaku, “The Universe in a Nutshell" (video)
- John Polinghorne, Quantum Theory: a very short introduction (pdf)
- Alan Lightman, Einstein’s Dreams (pdf).
- Stephen Hawking, The Universe in a Nutshell (pdf)
- Brian Greene, The Elegant Universe (pdf)
- Timothy Ferris, Coming of Age in the Milky Way (epub & mobi)
- Richard Feynman, QED: the strange theory of light & matter (pdf) and the Feynman Lectures on Physics (more technical).
- Douglas Hofstadter, Gödel, Escher, Bach: an eternal golden braid (pdf): also a MIT lecture series.
- Philosophy of time travel: “Time travel" and "Time travel & modern physics”, Stanford Encyclopedia of Philosophy; David Lewis, “The paradoxes of time travel" (paper); Theodore Sider, "Time travel: coincidences and counterfactuals" (paper); Jonathan Harrison, "Time travel for beginners" (paper); Frank Arntzenius, "Time travel: double your fun" (paper); Larry Dwyer, "Time travel and changing the past" (paper).
- Kip Thorne, Black Holes and Time Warps: Einstein’s Outrageous Legacy (pdf)
- J. Richard Gott, Time Travel in Einstein’s Universe
- Michael Lockwood, The Labyrinth of Time (pdf)
- Deutsch & Lockwood, “The Quantum Physics of Time Travel" (paper)
- Stephen Hawking, A Brief History of Time. Also Hawking’s lectures “Space Travel & Time Warps" and "Into A Black Hole”.
- Leonard Susskind, The Black Hole War: My Battle With Stephen Hawking (pdf): also a lecture.
- Seth Lloyd, “The Quantum Mechanics of Time Travel" (video) and Jim Al-Khalili, "Is Time Travel Possible?" (video)
The blare of human noise causes birds to pipe down and frogs to breed less frequently. Now, scientists have found a humanmade sound that has a far more colorful effect: The boom of a ship’s engine makes common cuttlefish (Sepia officinalis) change the complex swirls of skin hues, stripes, and spots that they use for camouflage and communication. Like other cephalopods such as octopus and squid, cuttlefish rely on visual and tactile signals to communicate; there’s been little evidence so far to suggest they perceive—or respond to—sound. But when researchers placed a loudspeaker near cuttlefish tanks and played the sound of an underwater engine, the animals swam more and changed colors more often. They also raised their first pair of arms, which are used to sense water movements, more frequently, the team reports in this month’s issue of The American Naturalist.
A previously unknown mechanism through which the brain produces new nerve cells after a stroke has been discovered at Lund University and Karolinska Institutet in Sweden. The findings have been published in the journal Science.
A stroke is caused by a blood clot blocking a blood vessel in the brain, which leads to an interruption of blood flow and therefore a shortage of oxygen. Many nerve cells die, resulting in motor, sensory and cognitive problems.
The researchers have shown that following an induced stroke in mice, support cells, so-called astrocytes, start to form nerve cells in the injured part of the brain. Using genetic methods to map the fate of the cells, the scientists could demonstrate that astrocytes in this area formed immature nerve cells, which then developed into mature nerve cells.
”This is the first time that astrocytes have been shown to have the capacity to start a process that leads to the generation of new nerve cells after a stroke”, says Zaal Kokaia, Professor of Experimental Medical Research at Lund University.
The scientists could also identify the signalling mechanism that regulates the conversion of the astrocytes to nerve cells. In a healthy brain, this signalling mechanism is active and inhibits the conversion, and, consequently, the astrocytes do not generate nerve cells. Following a stroke, the signalling mechanism is suppressed and astrocytes can start the process of generating new cells.
”Interestingly, even when we blocked the signalling mechanism in mice not subjected to a stroke, the astrocytes formed new nerve cells”, says Zaal Kokaia.
“This indicates that it is not only a stroke that can activate the latent process in astrocytes. Therefore, the mechanism is a potentially useful target for the production of new nerve cells, when replacing dead cells following other brain diseases or damage.”
The new nerve cells were found to form specialized contacts with other cells. It remains to be shown whether the nerve cells are functional and to what extent they contribute to the spontaneous recovery that is observed in a majority of experimental animals and patients after a stroke.
A decade ago, Kokaia’s and Lindvall’s research group was the first to show that stroke leads to the formation of new nerve cells from the adult brain’s own neural stem cells. The new findings further underscore that when the adult brain suffers a major blow such as a stroke, it makes a strong effort to repair itself using a variety of mechanisms.
The major advancement with the new study is that it demonstrates for the first time that self-repair in the adult brain involves astrocytes entering a process by which they change their identity to nerve cells.
”One of the major tasks now is to explore whether astrocytes are also converted to neurons in the human brain following damage or disease. Interestingly, it is known that in the healthy human brain, new nerve cells are formed in the striatum. The new data raise the possibility that some of these nerve cells derive from local astrocytes. If the new mechanism also operates in the human brain and can be potentiated, this could become of clinical importance not only for stroke patients, but also for replacing neurons which have died, thus restoring function in patients with other disorders such as Parkinson’s disease and Huntington’s disease”, says Olle Lindvall, Senior Professor of Neurology.
Texas wasp moth (Horama panthalon)
The Texas Wasp Moth is a moth of the Arctiidae family. It is found in South America, Central America, Mexico, the Antilles and southern United States. The wingspan is 32–34 mm (1.3–1.3 in). Adults are on wing year round. They mimic a paper wasp.
Everyone has heard of dyslexia, but do we truly understand what it means?
Infographic - by Weareteachers
EXERCISE is one of the best ways to protect against dementia in later life and the earlier you start, the greater the effect, research suggests.
Participating in intellectually stimulating leisure activities, paid work, volunteer work or study can also help protect against memory loss and reduce the risk of developing Alzheimer’s disease.
UWA adjunct clinical professor Nicola Lautenschlager, who led a review of strategies to delay cognitive decline, says there is a growing body of evidence that suggests exercise is beneficial for brain health.
"The knowledge we have so far basically makes it very clear that regular physical activity, even at an older age, can be very beneficial for protecting cognition," she says.
"Beyond that it’s also very effective for protecting or maintaining mental health, especially in relation to symptoms of depression or anxiety."
Prof Lautenschlager, who is based at the University of Melbourne, says older people who are well enough are advised to do 150 minutes of physical activity a week, such as going for walks.
"When it comes [to] brain health…it would be good if the walking speed isn’t very slow, so it shouldn’t be a stroll but rather what we call moderate pace," she says.
"Research has shown that the level of physical activity has to have a certain intensity so that the brain benefits."
Enjoyable hobbies key to brain health
Hobbies that keep the brain active, such as playing an instrument, going to concerts or joining a book club, can also be very helpful as long as it is an activity a person enjoys, Prof Lautenschlager says.
"The minute you prescribe an activity they hate doing…most likely the effect in terms of being beneficial for brain health is lost," she says.
"It produces so much stress in the body not wanting to do it that the stress is more harmful than the benefit of keeping the brain active."
Prof Lautenschlager says middle age is a crucial time for making lifestyle decisions that will determine a person’s health in later life.
"Usually we are talking about when you move into your 30s, definitely the 40s and also still the 50s," she says.
"Things like a high blood pressure or carrying too much weight, if you do that in these decades, it seems to harm the brain long-term in terms of how healthy a person is in their 70s or 80s."
Ideally people should aim for a healthy lifestyle from childhood but luckily research shows lifestyle changes still have an effect on brain health if a person is already old, Prof Lautenschlager says.
"Even programs…with seniors in their 70s and 80s can still make a difference," she says.
The research was published this month in the journal Maturitas.
Lonesome George, the Galapagos tortoise who was the last of his kind, is on view at the Museum through January 4, 2015. Below is a quick rundown of everything you need to know about Lonesome George.
Species: Last documented member of Chelonoidis abingdoni, native to Pinta Island
Age: Thought to be more than 100 years old
Diet: Cactus, shrubs, grasses, and broad-leaved plants
Turtle vs. tortoise? Tortoises are turtles that live exclusively on land.
Did you know? Lonesome George—the lone tortoise of his species for at least 40 years—was named after a famous 1950s American TV comedian, George Gobel, who called himself “Lonesome George.”
Notable traits: An extremely long neck and a “saddle-backed” shell that rises slightly in front, like a saddle
Weight: About 165 lbs (75 kg); males of various species of Galapagos tortoises can exceed 660 lbs (300 kg) and are the largest living tortoises
Discovery: In 1971, a Hungarian scientist spotted Lonesome George on Pinta Island. The discovery surprised researchers who thought Pinta Island tortoises were already extinct. A year later, George was taken to the Tortoise Breeding and Rearing Center on Santa Cruz Island, where he lived for the next 40 years.
Saving Lonesome George: Staff at the Galapagos National Park and Charles Darwin Research Station tried repeatedly to mate Lonesome George with females from closely related species. Those efforts failed, but a new strategy to revive the species is underway. The discovery of hybrid tortoises partially descended from Pinta Island tortoises on Isabela Island, where whalers or pirates likely moved them long ago, provides the opportunity for establishing a breeding colony whose young will initiate the recovery of a reproductive population on Pinta.
Can’t get enough Lonesome George info? Head to the Museum’s website for more.
leaf senescence begins with the advent of the summer solstice, as the days get shorter and sun becomes more distant. trees begin to reduce the production of chlorophyll — a green pigment critical to photosynthesis — and eventually begin to break down that which remains in the leaf in order to reabsorb its nitrogen.
as the green of leaves consequently begins to fade, other pigments in the leaf — carotenoids and flavonoids — also see reduced production in the leaf, but at a much slower rate than chlorophyll, which enables their yellow and orange colours to be expressed.
for some trees, colder temperatures trigger the synthesis of the flavonoid anthocyanin, causing those leaves with lower levels of other flavonoids or carotenoids to turn red. if other pigments are sufficiently present, the colours can blend into auburn.
it is believed that trees will produce anthocyanin to protect themselves from sap sucking insects that would otherwise be drawn to the yellow and orange colours of their leaves.
eventually, these non chlorophyll pigments fade themselves as the tree, in preparation for winter, denies its leaves water (otherwise transported through some of the veins seen here). in an effort to also retain nutrients, a deciduous tree will then signal the abscission cells at the base of its leaves to swell.
this not only blocks the flow of nutrients but ultimately causes the leaves to tear away and fall to the ground, where the tree can then reabsorb any leaf nutrients through its roots before going into winter dormancy.
Right now as your sitting/lying down, you’re actually moving at 1000 miles per hour. To make one complete rotation around in 24 hours, the earth spins at 1000 miles per hour or 1600 km/hr. Because gravity holds us so tight & we move with the Earth, we don’t notice it.
In addition to spinning on its axis, the Earth also revolves around the Sun. It takes us one year (365 days) to go around once. The full path of the Earth’s orbit is close to 600 million miles (970 million km). To go around this immense circle in one year takes a speed of 66,000 miles per hour (107,000 km/hr). At this speed, you could get from San Francisco to Washington DC in 3 minutes. (Source)