  Anomalies from the LHCb lepton flavour universality and Fermilab muon
anomalous magnetic momentum, show tantalizing hints of possible new physics
from the lepton sectors. Due to its large mass and shorter lifetime than muon,
the tau lepton is believed to couple more to possible new physics beyond the
standard model. Traditionally, tau leptons are probed through the decay
products due to tau's short life time. On the other hand, at a high energy
scale, a large fraction of tau leptons could be boosted to a much longer life
time and fly a visible distance from several centimetres up to kilometer length
scale, yet very informative to new physics beyond the standard model or high
energy cosmic rays. In this article, we show unique yet promising tau physics
by exploiting long-lived taus as a microscope or macroscope, to measure tau's
anomalous magnetic momentum to an unprecedented level of accuracy and detect
high energy cosmic neutrinos at the 1 TeV to 1 PeV scale, respectively.
